WE-G-213CD-03: A Dual Complementary Verification Method for Dynamic Tumor Tracking on Vero SBRT

Area of Science:

• Medical Physics
• Radiation Oncology
• Image-Guided Therapy

Background:

• Accurate tumor tracking is crucial for Stereotactic Body Radiation Therapy (SBRT).
• Dynamic tracking (DT) systems require robust methods for real-time accuracy verification.
• Existing methods may not fully capture in-vivo performance during treatment delivery.

Purpose of the Study:

• To evaluate the accuracy of in-vivo tumor tracking using complementary cine Electronic Portal Imaging Device (EPID) and gimbal log file analysis.
• To validate the reliability of gimbal log files for monitoring tracking accuracy on the Vero SBRT system.
• To assess the clinical applicability of this combined approach for dynamic tracking.

Main Methods:

• Integrated a clinical prototype of dynamic tracking (DT) with gimbal log file analysis and cine EPID on the Vero SBRT system.
• Quantified tracking error using cine EPID (E-EPID) and gimbal log files combined with x-ray verification (E-kVLog).
• Validated gimbal log file accuracy by correlating E-kVLog with E-EPID and testing sensitivity to introduced systematic errors.

Main Results:

• A strong correlation (R=0.98) was observed between gimbal log file and cine EPID tracking error measurements.
• Gimbal log files demonstrated sensitivity to detect systematic tracking errors as small as 0.5 mm.
• Dynamic hidden target tests confirmed no gravity influence and decoupled gimbal/gantry rotation, showing submillimetric agreement.

Conclusions:

• The integration of gimbal log files with cine EPID provides a redundant and accurate method for monitoring tumor tracking accuracy in Vero SBRT.
• This complementary approach enhances the reliability and clinical safety of dynamic tracking systems.
• The study confirms the feasibility and effectiveness of using log file data for real-time treatment verification.